Sucking your kid's pacifier to clean it: good for immunity or gross?

A baby pacifier hangs from an umbrella as part of the props used by union workers in a non-profit sector march in Brussels December 2, 2005. (Reuters)

Toddlers are less likely to have asthma and itchy rashes if their parents "cleaned" their pacifiers by sucking on them when the kids were infants, a small new study suggests.

The findings don't prove that technique protects kids against asthma, eczema or other allergies. But researchers said it's possible the transfer of mouth microbes from parents to baby may help boost the bacterial diversity of the young child's digestive system and foster immunity.

"We know these bacteria are important for development," said Dr. Wilfried Karmaus from the University of Memphis, who has studied asthma and eczema but wasn't involved in the new research.

Being delivered through a vaginal birth, for example, exposes babies to more of their moms' bacteria and has been linked to fewer allergies in childhood. But no one has ever looked at transfer of bacteria through pacifiers, Karmaus said.

For the new study, researchers recruited pregnant women at one Swedish hospital and followed them and their children through phone calls and exams over three years. The 184 infants in the study were particularly allergy-prone: 80 percent had at least one parent with allergies.

When the babies were six months old, 65 parents reported "cleaning" their pacifiers by sucking on them. Most parents also said they rinsed pacifiers with tap water.

The children were then brought in for allergy testing at 18 and 36 months of age.

At the first visit, 46 of them had eczema and 10 had asthma symptoms.

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Kids whose pacifiers had been sucked on by parents were 63 percent less likely to have eczema at 18 months and 88 percent less likely to have asthma, compared to the children of parents who didn't use that cleaning technique.

By 36 months, the difference had gone away for asthma. Parental pacifier sucking was still tied to a 49-percent lower chance of a child having eczema, researchers led by Dr. Bill Hesselmar from Queen Silvia Children's Hospital in Gothenburg found.

There was no clear link between parents' pacifier cleaning method and babies' sensitization to common allergens, such as cat and dog dander or eggs and peanuts, at either age.

In a smaller analysis of 33 infants, the researchers found that babies whose parents did or didn't suck on their pacifiers had different types of bacteria living in their mouths, the group reported Monday in Pediatrics.

"With the different oral flora, it supports the hypothesis and the findings," Hesselmar told Reuters Health.

Still, he said the study can't prove the pacifier cleaning method protected kids against asthma and eczema, and that it's too early to recommend this technique to parents.

"It's always hard to tell if it's the only explanation, but we have tried to analyze as many other possibilities as we can think of," he said.

"This is a simple measure which is really, really nice," Karmaus said. "But we need a trial to be really sure that this is protective."

A gold-standard trial would involve randomly assigning some parents to regularly clean pacifiers by sucking on them and others to never use that method. In the current study, Karmaus said, it's possible parents who decided on their own to suck on their child's pacifier were different from parents who didn't in other important, allergy-related ways.

"It could be that these parents have more time with their children, a less stressful relationship with their children, hug their children more or whatever," he told Reuters Health.

For now, he said, parents should know that using their mouth to clean an infant's pacifier may be worth trying - and at the very least, shouldn't be harmful.

That technique may also be a necessity from time to time, Karmaus noted.

"Sometimes you take two or three pacifiers with you but if all are dirty and your child is crying, there's nothing you can do" but clean it yourself.